Opt-outs have become commonplace in baseball, with J.D. Martinez and David Price among the more high-profile players to have them baked into their deals.
Harper, speaking as a member of the Phillies for the first time on Saturday, was asked about the lack of such a clause.
"This guy (agent Scott Boras) invented the opt-out," Harper said. "I told him at the beginning of the process I didn't want one wherever I went. I wanted to dig my roots in."
Harper added that he wanted to commit to being part of building and maintaining a winning ballclub.
"I don't want to go anywhere else ... Through the bumps and bruises, the good and the bad, I'm going to be here."
Boras echoed his client's statements, explaining that Harper wants to recruit players to a city and isn't looking to leave town.
Harper was also asked during the introductory press conference why he decided to change his number from No. 34 to No. 3. He said he thought right-hander Roy Halladay, recently elected posthumously to the Hall of Fame, should be the last Phillies player to wear 34.
Harper may have had ulterior motives in signing with the Phillies, too.